What to do if your car heater isn't working

Jack Dreyer | Thursday 13th October 2022 12:00pm

Hand placed near a car's heater vents to see if they're working.

While itís normal for air con to stop working at the most inconvenient times (midsummer noon in a traffic jam) Ė if your carís heater stops working then you should pay attention: it could indicate a more serious problem. So donít put off car checks if your car heaterís blowing out cold air.

Letís first quickly look at how a heater works.

How does a car heater work?

a car's coolant reservoir, part of the heating and cooling system sits in an engine bay, seemingly with the right level of coolant.

Weíll not go into the complete technical detail, but itís worth knowing that your air con and heating system are related. Essentially, theyíre both ways of using the heat and power generated by your engine to either cool or warm air thatís circulated around your vehicle.

Air con works slightly differently in that you need a refrigerant to get the air lower than the ambient air temperature, but car heaters are (in most vehicles) essentially just the engine.

The engine needs to get up to a certain operating temperature to run most efficiently, but after a certain point itís liable to overheat. Original car designs featured grills to cool the engine with air directed to it while the car drives Ė but what about when youíre stuck in traffic? Or what about when itís an extremely hot summerís day?

Quite soon, liquid cooling was invented to help regulate engines at all times.

The fundamental concept here is that a coolant liquid is pumped through tubes that are around the engine, the liquid is warmed by the heat of the engine (therefore taking heat out of the engine), and then it is released somewhere through the use of a radiator.

The coolant liquid here forms a closed loop system, so as it circulates itís constantly drawing heat away from the engine.

Car heaters are an extra addition to this loop. The idea is that an extra radiator is added into the loop Ė that radiator is placed in front of a fan that pulls air into the ducts (either from the outside or from inside the car) and past the radiator into the vehicle itself. As the cold air passes over the now-hot radiator, itís warmed up.

This is why it often takes a few minutes for the heating in your car to get going Ė because it takes a few minutes for the engine and coolant to get warm!

What does it mean if your car heating stops working?

Person in car attempting to warm up with broken heating.

It can mean a few things depending on which part seems to have stopped working.

1.) The fan may have broken or the ducts may have become blocked

If youíve turned the heating on but thereís no air coming through open ducts, then thereís a good chance that the problem lies with the radiator fan. Check the air grills around the outside of your car, specifically around the air intake vent.

2.) There could be a coolant leak

If the fans are running as normal at all powers, then you need to check your coolant reservoir to make sure the coolant level hasnít dropped. If the air isnít getting hot then itís possible that the coolant has leaked to a point where thereís not enough to even cool the engine.

In this situation, your first step should be to turn off the engine and try topping up the reservoir (slowly) with more coolant.

Hopefully, itíll only be a slow leak so that youíve got time to get to a service centre!

If the coolant quickly drains then youíve got a bigger problem on your hands because you shouldnít drive your car without coolant Ė an overheated engine is potentially a much more costly fix than a few pipes!

Your best bet here is to call for emergency assistance to have your car towed to an auto centre.

Trust the experts at your local Kwik Fit centre

We hope you never have to call for roadside assistance, and we strive to help you never need to through our range of services: from 6-monthly checkups to full-blown part replacements, you can trust the experts at your local Kwik Fit to keep your car sturdy.

Any facts, figures and prices shown in our blog articles are correct at time of publication.

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